If a control key is added on top of the keyboard (as suggested in #1), this still leaves three smaller key spaces on the top unused. If they could be user-assignable, the keyboard would become more ergonomic for speakers of languages close to English but with slightly larger alphabets, e.g. the Nordic languages. These people urrently have to long press letter keys which is slow and cumbersome.

I recognise that the real answer may be "but these languages should get a fully optimised layout of their own" but I disagree. I prefer learning a standard layout variant and making small tweaks over learning a fully different layout. This community is small enough without splintering it further!